ERPs reveal comparable syntactic sentence processing in native and non-native readers of English.

L2 syntactic processing has been primarily investigated in the context of syntactic anomaly detection, but only sparsely with syntactic ambiguity. In the field of event-related potentials (ERPs) syntactic anomaly detection and syntactic ambiguity resolution is linked to the P600. The current ERP experiment examined L2 syntactic processing in highly proficient L1 Spanish-L2 English readers who had acquired English informally around the age of 5 years. Temporary syntactic ambiguity (induced by verb subcategorization information) was tested as a language-specific phenomenon of L2, while syntactic anomaly resulted from phrase structure constraints that are similar in L1 and L2. Participants judged whether a sentence was syntactically acceptable or not. Native readers of English showed a P600 in the temporary syntactically ambiguous and syntactically anomalous sentences. A comparable picture emerged in the non-native readers of English. Both critical syntactic conditions elicited a P600, however, the distribution and latency of the P600 varied in the syntactic anomaly condition. The results clearly show that early acquisition of L2 syntactic knowledge leads to comparable online sensitivity towards temporal syntactic ambiguity and syntactic anomaly in early and highly proficient non-native readers of English and native readers of English.